An X-ray CT (computed tomography) apparatus is an apparatus which scans an object (patient) using X-rays, processes collected data using a computer, and thereby produces images of the patient's interior. Specifically, the X-ray CT apparatus exposes the patient to X-rays multiple times from different directions along a circular orbit around the object. The X-ray CT apparatus detects the X-rays transmitted through the object and collects plural items of detection data. The collected detection data is subjected to A/D (analog to digital) conversion by a data collection unit and then sent to a console apparatus.
The console apparatus generates projection data by pre-processing the detection data. Thereafter, the console apparatus performs a reconstruction process based on the projection data and generates tomographic data as well as volume data which is based on plural items of tomographic data. The volume data is a data set which represents a three-dimensional distribution of CT values corresponding to a three-dimensional area of the object.
The X-ray CT apparatus can create an MPR (multi planar reconstruction) display by rendering the volume data in any desired direction. Hereinafter, a sectional image whose MPR display has been created by rendering volume data is sometimes referred to as an “MPR image.” Examples of MPR images include an axial image which shows an orthogonal section with respect to a body axis, a sagittal image which shows a section obtained by cutting the object straight along the body axis, and a coronal image which shows a section obtained by cutting the object across the body axis. Furthermore, the MPR images may include an image (oblique image) of an arbitrary cross section in volume data. Plural MPR images generated are displayed simultaneously on a display unit or the like.
A method is available which performs computed tomography fluoroscopy (CTF) using an X-ray CT apparatus. The CT fluoroscopy is a method for obtaining CT images of a region of interest in an object in real time (sequentially) by irradiating the patient continually with X-rays. The CT fluoroscopy generates real-time CTF images by increasing a collection rate of detection data and thereby reducing the time required for a reconstruction process. For example, the CT fluoroscopy is used for localization of a puncture target in a puncture procedure.
However, with conventional techniques, which do not change a fluoroscopic coverage during a puncture procedure which uses CT fluoroscopy, even a part which is located outside a periphery of a puncture needle tip and less relevant to the puncture procedure is irradiated with X-rays, posing a problem of unnecessary exposure of the patient to X-ray radiation.
That is, as long as the fluoroscopic coverage does not change during the puncture procedure which uses CT fluoroscopy, there remains a problem from the perspective of health hazards to the patient.